What Causes Pain In Nipple Piercing?

I am a 51 yr old male who had his nipples pierced in August 2010. They have been uneventful until the last week. My girlfriend played with them quite a bit last week and the right one has been very sore, to the point of me not wanting her to even touch it. I have used long hot salt water (non-iodized) soaks when I take my bath at night for the last two nights. Still no relief. It is at it's worst when I flip the ring upward, rotating in the channel. I can easily move the ring left and right inside the channel, with lesser pain. There was a small "crustie" on one side 3 days ago, just like when I first had it done. That is the only sign of discharge that I have. Any ideas?